Ion trap mass spectrometers with space charge control

Abstract

A method of mass spectrometry or ion mobility spectrometry is disclosed comprising: providing ions towards an ion storage region; selecting a target maximum charge desired to be stored within the ion storage region at any given time; and reducing the ion current passing to the ion storage region such that the ions entering the ion storage region do not cause the total charge within the storage region to rise above said target maximum charge. The step of reducing the ion current passing to the ion storage region comprises: temporally separating the ions according to their ion mobility in an ion mobility separator; and mass filtering the ions according to mass to charge ratio with a mass filter. Said steps of separating and mass filtering the ions result in substantially only target ions having selected combinations of ion mobility and mass to charge ratio being transmitted towards the ion storage region. The method further comprises accumulating the target ions within the ion storage region during an ion accumulation period.

Description

CROSS REFERENCE TO RELATED APPLICATION APPLICATIONS[0001]This application is the National Stage of International Application No. PCT / GB2014 / 053334, filed 11 Nov. 2014 which claims priority from and the benefit of United Kingdom patent application No. 1319942.7 filed on 12 Nov. 2013 and European patent application No. 13192561.2 filed on 12 Nov. 2013. The entire contents of these applications are incorporated herein by reference.BACKGROUND TO THE PRESENT INVENTION[0002]The present invention provides a method of mass spectrometry and a mass spectrometer.[0003]Many mass or ion mobility spectrometers include ion trapping devices. The performance of such ion trapping devices can vary greatly due to detrimental space charge effects, the effects of which vary depending on the amount of charge accumulated within the ion trap. The detrimental effects can range from loss of mass accuracy, through loss of resolution, ultimately to loss of signal as ions ‘overflow’ from the ion trap and are los...

AI Technical Summary

Benefits of technology

The present invention improves the sensitivity of ion trapping devices by reducing the ion current and enriching target ions of interest within the device. This is achieved by controlling the mass filter to filter out ions that could cause the number of ions within the reaction region to rise above the target maximum charge.

Problems solved by technology

The performance of such ion trapping devices can vary greatly due to detrimental space charge effects, the effects of which vary depending on the amount of charge accumulated within the ion trap.

The detrimental effects can range from loss of mass accuracy, through loss of resolution, ultimately to loss of signal as ions ‘overflow’ from the ion trap and are lost.

This loss of signal can be both mass to charge ratio dependent and charge dependent, rendering the correction of such effects difficult.

However, whilst these approaches have proven useful, they fundamentally reduce the sensitivity of the system.

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